1. Field of the Invention
The present invention relates to a timepiece, such as a watch, wristwatch, clock, or the like, in which time is indicated by indication members such as hands or the like, mounted on gears, which form a gear train, and which comprises a time correction mechanism operated by an external operation member transmitting an external operating force to the inside of the timepiece.
2. Description of the Related Art
Conventionally, there have been used timepieces, in which hands rotating at predetermined rotating speeds point to numerals or graduations marked on a dial.
Generally, such timepieces are provided with a time correction mechanism, which permits manual operation to rotate hands for the purpose of correction of the indicated time.
As disclosed in JP-B-8-27360, a time correction mechanism has been known, in which a clutch plate is movably provided to engage with a shaft of a third gear provided with a pinion adapted to mesh with a second gear.
With such time correction mechanism, when a winding stem is pulled out to move the clutch plate, a posture of the third gear is inclined to separate the pinion of the third gear from the second gear, so that meshing of the second gear and the third gear is released. Thereby, a force of rotating operation applied on the winding stem for correction of time is not transmitted to a mechanism of speed regulation provided on the third gear or a succeeding gear, whereby it is possible to freely carry out an operation of time correction.
The time correction mechanism comprises a slot formed in the clutch plate, a positioning pin inserted through the slot, and an engagement projection engageable with the positioning pin and arranged on a central portion in a longitudinal direction of the slot.
When the clutch plate is to be moved, the engagement projection provided on the slot engages with the positioning pin, so that the clutch plate is not moved unless a somewhat large operating force is applied.
Thereby, the clutch plate is not moved inadvertently, so that it can be held in two predetermined positions except for intended operation and advancing and retreating motions of a winding stem can be made moderate.
With such time correction mechanism, since forces, with which the winding stem is pulled out or in, cause movement of the clutch plate and a somewhat large operating force is necessary for operation of the winding stem, there is caused a problem that large forces are in some cases applied on the winding stem and the clutch plate, and so strength for the winding stem and the clutch plate must be adequately ensured, by which it is necessary to adequately increase a diameter of the winding stem and a thickness dimension of the clutch plate, thereby causing a problem that thin sizing and miniaturization of the timepiece are impeded.
Besides, there is also caused a problem that when it is tried to surely hold the clutch plate in either of the two predetermined positions, a large force is made necessary in operation of the winding stem, and a smooth operation of the winding stem becomes difficult, so that an uncomfortable feeling results in operation.
FIG. 7 shows a clutch plate 80 for solving the above-mentioned problem. That is, the clutch plate 80 pivotally supports a shaft 3c (FIG. 8) on a side of a pinion 3b of a third gear 3 as shown in FIGS. 7 and 8. In addition, a shaft 3d on a side of a gear 3a of the third gear 3 is pivotally supported on a gear train bridge 9. Also, the reference numeral 8 in FIG. 8 denotes an hour gear.
The clutch plate 80 is supported by a rotating shaft 11, which is provided upright on a main plate 10, so as to be able to turn between a first angular position A, in which a gear 2a of a second gear 2 and the pinion 3b of the third gear 3 mesh with each other, and a second angular position B, in which meshing of the gear 2a of the second gear 2 and the pinion 3b of the third gear 3 is released but meshing of the gear 3a and a pinion 4b of a fourth gear 4 is not released.
Provided on the main plate 10 are a projection 12 for restricting a position of an abutment 81 of the clutch plate 80 so as to prevent the clutch plate from turning further in a clockwise direction in the figure from the first angular position A, and a projection 13 for restricting a position of a tip end 20A of the clutch plate 80 so as to prevent the clutch plate from turning further in a counterclockwise direction in the figure from the second angular position B.
Here, the abutment 81 of the clutch plate 80 is provided with an abutment surface 81A adapted to abut against the projection 12. The abutment surface 81A serves to restrict turning of the clutch plate 80, and so extends radially of the rotating shaft 11 of the clutch plate 80, that is, perpendicularly to a turning direction of the clutch plate 80 and obliquely intersects a straight line α connecting between the centers of rotation of the second gear 2 and the third gear 3.
Provided on the clutch plate 80 are a first elastic deformation portion 22 generating an elastic force to bias the abutment 81 of the clutch plate 80 in a direction toward the projection 12, and a second elastic deformation portion 23 generating an elastic force to bias the abutment 81 of the clutch plate 80 in a direction away from the projection 12.
Here, a winding stem 14 is provided to be able to advance or retreat from an interior of a timepiece 1 to cause elastic deformation of the first elastic deformation portion 22 in an advance position C to generate an elastic force and to return the first elastic deformation portion 22 in a retreat position D to an original state to lessen the elastic force.
In other words, when the winding stem 14 advances, an elastic force of the first elastic deformation portion 22 resists an elastic force of the second elastic deformation portion 23 to turn the clutch plate 80 to the first angular position A. In a state, in which the clutch plate 80 is positioned in the first angular position A, the third gear 3 makes the rotating shaft vertical as shown in FIG. 8 to have its pinion 3b meshing with the teeth 2a of the second gear 2.
Meanwhile, when the winding stem 14 retreats, an elastic force of the second elastic deformation portion 23 causes the clutch plate 80 to turn to the second angular position B. In a state, in which the clutch plate 80 is positioned in the second angular position B, the third gear 3 makes the rotating shaft oblique as shown by alternate long and two short dashes lines in FIG. 8 to release meshing of the pinion 3b and the teeth 2a of the second gear 2. However, meshing of the gear 3a and the pinion 4b of a fourth gear 4 is not released.
Since adoption of such clutch plate 80 causes elastic forces of the first elastic deformation portion 22 and the second elastic deformation portion 23 to move the clutch plate 80, the winding stem 14 can be operated with a small force and large forces are not applied on the winding stem 14 and the clutch plate 80, so that it is possible to set a diameter of the winding stem 14 and a thickness dimension of the clutch plate 80 to small values, which contributes to thinness and minimization of the timepiece 1.
Besides, no large force is necessary to operate the winding stem 14, so that the winding stem 14 can be smoothly operated to provide a comfortable feeling during operation.
However, a time correction mechanism adopting the clutch plate 80 involves the following problems.
That is, the projection 12 does not restrict displacement of the abutment 81 in a direction along the abutment surface 81A as shown in FIG. 9 and the straight line α connecting between centers of rotation of the second gear 2 and the third gear 3 obliquely intersects the abutment surface 81A, so that when the clutch plate 80 is deformed, the projection 12 and the abutment 81 allow displacement of the third gear 3 in a direction along an arrow β as shown in FIG. 9.
Therefore, there is caused a problem that when the clutch plate 80 is deformed upon a shock due to falling, or the like, a distance between centers of rotation of the second gear 2 and the third gear 3 is decreased making meshing of the pinion 3b of the third gear 3 and the teeth 2a of the second gear 2 deep, so that the rotating drive resistance of the second gear 2 and the third gear 3 becomes large, which increases in loss of mechanical energy and which negatively results in the timepiece being stopped.
Also, formed on the clutch plate 80 as shown in FIG. 10 is an engagement 84 being an engaging portion to engage with the winding stem 14. The engagement 84 is formed with an engaging surface 84A to engage with the winding stem 14. Since the engaging surface 84A is defined by a planar plane in contact with an outer peripheral surface of the columnar-shaped winding stem 14, there is also caused a problem that upon the rotating operation of the winding stem 14, the engagement 84 of the clutch plate 80 is moved in the rotating direction of the winding stem 14 and so an intended action cannot be carried out even when the winding stem 14 is operated.